In February this year, Envia released more details of its technology, claiming an energy density of 400 watt-hours per kilogram--far more than the 140 watt-hours per kilogram offered by the battery pack in the 2012 Nissan Leaf.

The more energy an electric car battery can store for a given weight, the larger its capacity and the further the car can travel.

As Akerson pointed out back in March, an energy-density increase from existing battery technology could mean a car like the Chevrolet Volt could travel as far as 140 miles on a battery pack the same physical size as its current battery pack.

Or, it could cut the size, weight, and cost of the car's current 16-kWh pack substantially while maintaining the existing 38-mile range of the 2013 Volt.